1. Technical Field
The present invention relates to an image processing device, an image processing method, and a computer readable medium.
2. Related Art
A technique for matching process involves judging whether or not two images are matched. Two techniques are provided as follows.
(1) Technique for detecting a known pattern from the image. For example, this technique is used for inspection of character or graphic printed on a printed board or the like.
(2) Technique for compressing the document based on the matching process. For example, this technique is performed by extracting the character or graphic element from the image, registering the pattern extracted as a result of the matching process in a dictionary, and encoding the rendering position of image and pattern in the dictionary. A specific example is a process for the text region (Text Region) in the JBIG2 (ITU-T T.88).
In the case of (1), the image size of comparison object is generally fixed.
In the case of (2), the matching process for character and graphic images of any size has to be performed.
And in the case of (2), the matching process for character and graphic images of any size mainly uses a combination of the following two methods.
(2.1) Global Template Matching (Global Template Matching)
The matching process compares the feature amount of the overall image (area, perimeter, center of gravity, moment, number of pores, etc.) between two images. It has the characteristics that because the detailed feature of the image is lost, the matching performance is worse but the computation amount is small.
(2.2) Local Template Matching (Local Template Matching)
The matching process compares the local feature amount (density, pixel distribution, etc.) between two images. It has the characteristics that the matching performance is high but the computation amount is large.
Generally, the global template matching as the screening (coarse sieve) and the local template matching as the minute matching are used jointly.